Treatment of environmental contaminants

ABSTRACT

Contaminants, such as volatile organic compounds, are removed from an environmental medium, such as contaminated soil, rock, groundwater, waste water and the like, by treatment with a combination of a persulfate, such as a sodium persulfate, and hydrogen peroxide.

This application claims the benefit of U.S. Provisional Application No.60/491,007, filed Jul. 29, 2003.

FIELD OF THE INVENTION

The present invention relates to the in situ and ex situ oxidation oforganic compounds in soils, groundwater, process water and wastewaterand especially relates to the in situ oxidation of volatile andsemi-volatile organic compounds, pesticides and other recalcitrantorganic compounds in soil and groundwater.

BACKGROUND OF THE INVENTION

The presence of volatile organic compounds (VOCs), semi-volatile organiccompounds (SVOCs), pesticides, polychlorinated biphenyls (PCBs),polyaromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs)in subsurface soils and groundwater is a well-documented and extensiveproblem in industrialized and industrializing countries. Notable amongthese are the volatile organic compounds or VOCs which include any atleast slightly water soluble chemical compound of carbon, with a Henry'sLaw Constant greater than 10.sup.-7 atm m.sup.3/mole, which is toxic orcarcinogenic, is capable of moving through the soil under the influenceof gravity and serving as a source of water contamination by dissolutioninto water passing through the contaminated soil due to its solubility,including, but not limited to, chlorinated solvents such astrichloroethylene (TCE), vinyl chloride, tetrachloroethylene (PCE),methylene chloride, 1,2-dichloroethane, 1,1,1-trichloroethane (TCA),1,1-dichloroethane, 1,1-dichloroethene, carbon tetrachloride, benzene,chloroform, chlorobenzenes, and other compounds such as ethylenedibromide, and methyl tertiary butyl ether.

In many cases discharge of VOCs and other contaminants into the soilleads to contamination of aquifers resulting in potential public healthimpacts and degradation of groundwater resources for future use.Treatment and remediation of soils contaminated with VOCs and otherorganic contaminants have been expensive, require considerable time, andin many cases are incomplete or unsuccessful. Treatment and remediationof compounds that are either partially or completely immiscible withwater (i.e., Non Aqueous Phase Liquids or NAPLs) have been particularlydifficult. Also treatment of highly soluble but biologically stableorganic contaminants such as MTBE and 1,4-dioxane are also quitedifficult with conventional remediation technologies. This isparticularly true if these compounds are not significantly naturallydegraded, either chemically or biologically, in soil environments. NAPLspresent in the subsurface can be toxic to humans and other organisms andcan slowly release dissolved aqueous or gas phase volatile organiccompounds to the groundwater resulting in long-term (i.e., decades orlonger) sources of chemical contamination of the subsurface. In manycases subsurface groundwater contaminant plumes may extend hundreds tothousands of feet from the source of the chemicals resulting inextensive contamination of the subsurface. These chemicals may then betransported into drinking water sources, lakes, rivers, and evenbasements of homes through volatilization from groundwater.

The U.S. Environmental Protection Agency (USEPA) has established maximumconcentration limits for various hazardous compounds. Very low andstringent drinking water limits have been placed on many halogenatedorganic compounds. For example, the maximum concentration limits forsolvents such as trichloroethylene, tetrachloroethylene, and carbontetrachloride have been established at 5 .mu.g/L, while the maximumconcentration limits for chlorobenzenes, polychlorinated biphenyls(PCBs), and ethylene dibromide have been established by the USEPA at100.mu.g/L, 0.5.mu./L, and 0.05.mu.g/L, respectively. Meeting thesecleanup criteria is difficult, time consuming, costly, and oftenvirtually impossible using existing technologies.

Many methods exist for the remediation of soil, groundwater andwastewater to meet the clean-up standards. Examples includedig-and-haul, pump-and-treat, biodegradation, sparging, and vaporextraction. However, meeting stringent clean-up standards is oftencostly, time-consuming, and often ineffective for many compounds thatare recalcitrant—i.e. not responsive to such treatment.

Chemical oxidation, either applied in situ or ex situ of the subsurfaceor waste stream, is an approach to treat contaminants with strongoxidizing chemicals, with the ultimate goal of complete mineralization,or conversion to carbon dioxide and water. Examples of oxidants thathave been utilized for this purpose include Fenton's chemistry(activated hydrogen peroxide), permanganate and ozone. Persulfates, andin particular sodium persulfate, have more recently been suggested foruse in environmental remediation through chemical oxidation.

The use of hydrogen peroxide, and in particular metal-activated hydrogenperoxide (Fenton's chemistry) has been employed in the field applicationof chemical oxidation remediation over the past decade. Metals andchelated metals have been utilized to generate hydroxy radicals, whichare capable of destroying a wide range of contaminants. However, thereis significant demand on the hydrogen peoxide form nascent organics inthe soil or groundwater, and from reduced metals. Thus, a significantamount of the hydrogen peroxide is expended on non-critical reactionpathways. In addition, transportation of the metal activators within theenvironmental medium is a key technological factor in the efficient useof hydrogen peroxide as an oxidant. Also, there is little datademonstrating that Fenton's chemistry is effective against highlyrecalcitrant contaminants.

SUMMARY OF THE INVENTION

The present invention relates to a method for the treatment ofcontaminated soil, sediment, clay, rock, and the like containing organiccontaminants, as well as the treatment of groundwater, process water orwastewater containing organic contaminants.

The method of the present invention uses a combination of water solubleoxidants, namely a persulfate and hydrogen peroxide. The combination isintroduced into soil or water in amounts, under conditions and in amanner which assures that the oxidizing compounds are able to contactand oxidize most, and preferably substantially all, the targetcontaminants rendering the target contaminants harmless.

In a preferred embodiment the composition of the present invention isintroduced into soil in sufficient quantities to satisfy the soiloxidant demand and to oxidize the target contaminants and render themharmless. This methodology may also be used ex situ to treat quantitiesof contaminated soil which have been removed from the ground.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the present invention it has been found that a broadrange of contaminants in an environmental medium can be effectivelyreduced or removed by treatment with a composition comprising apersulfate and hydrogen peroxide. Further improvements have been foundwhen an activator is included in the composition.

Contaminants susceptible to treatment by the compositions of the presentinvention include: volatile organic compounds (VOCs); semi volatileorganic compounds (SVOCs); polychlorinated biphenyls (PCBs);polyaromatic hydrocarbons (PHHs); total petroleum hydrocarbons (TPHs)including benzene, toluene, xylene and ethylbenzene; methyl t-butylether (MTBE); brominated solvents; 1,4-dioxane; and pesticides(insecticides, herbicides, etc.).

In accordance with the method of the present invention the contaminantsare treated in an environmental medium. As used herein “environmentalmedium” refers to an environment where contaminants are found including,without limitation, soil, rock, groundwater, contaminated plumes,process water, waste water and the like.

The process of the present invention may be carried out in situ or exsitu. In situ treatment is conducted in the physical environment wherethe contaminant(s) are found.

Ex situ treatment involves removal of the contaminated medium from thelocation where it is found and treatment at a different location.

In accordance with one embodiment of the present invention, theoxidation of volatile organic compounds at a contaminated site isaccomplished by the injection of a combination of a persulfate andhydrogen peroxide into soil.

In a preferred form of the invention, sodium persulfate (Na₂S₂O₈) isintroduced into contaminated soil along with hydrogen peroxide.

For in situ soil treatment, injection rates must be chosen based uponthe hydro geologic conditions, that is, the ability of the oxidizingsolution to displace, mix and disperse with existing groundwater andmove through the soil. Additionally, injection rates must be sufficientto satisfy the soil oxidant demand and chemical oxidant demand in arealistic time frame. It is advantageous to clean up sites in both acost effective and timely manner. Careful evaluation of site parametersis crucial. It is well known that soil permeability may change rapidlyboth as a function of depth and lateral dimension. Therefore, injectionwell locations are also site specific. Proper application of anyremediation technology depends upon knowledge of the subsurfaceconditions, both chemical and physical, and this process is notdifferent in that respect.

While sodium persulfate is the preferred persulfate compound foroxidizing the contaminants, other solid phase water soluble persulfatecompounds can be used. These include monopersulfates and dipersulfates.Dipersulfates are preferred because they are inexpensive and survive forlong periods in the groundwater saturated soil under typical siteconditions.

The most preferred dipersulfate is sodium persulfate as it has thegreatest solubility in water and is least expensive. Moreover, itgenerates sodium and sulfate upon reduction, both of which arerelatively benign from environmental and health perspectives. Potassiumpersulfate and ammonium persulfate are examples of other persulfateswhich might be used. Potassium persulfate, however, is an order ofmagnitude less soluble in water than sodium persulfate; and ammoniumpersulfate is even less desirable as it may decompose into constituentswhich are potential health concerns.

In accordance with the present invention the persulfate is used incombination with hydrogen peroxide.

The hydrogen peroxide may contain an organic or inorganic compound suchas phosphoric acid, which can generate hydrogen ions. The hydrogenperoxide may be introduced into the soil, groundwater or wastewater,either in combination with the persulfates, or sequentially, eitherbefore, after or in repeated sequential steps to the persulfateintroduction. Enough of the persulfate and hydrogen peroxide need to beintroduced to overcome the soil oxidant demand and to reduce theconcentration of the contaminants to the desired levels.

The amounts of oxidants used are not critical, except it is preferredthat enough is present to satisfy substantially all the soil oxidantdemand and to remove the contaminants to acceptable levels, or as closethereto as possible. Thus, any amount within a mole ratio of persulfateto hydrogen peroxide of from 1:20 to 20:1 may be used. Preferred resultsare achieved with a mole ratio of persulfate to hydrogen peroxide offrom 1:10 to 10:1.

The preferred concentrations are a function of the soil characteristics,including the site-specific oxidant demands. Hydrogeologic conditionsgovern the rate of movement of the chemicals through the soil, and thoseconditions must be considered together with the soil chemistry tounderstand how best to perform the injection. The techniques for makingthese determinations and performing the injections are well known in theart. For example, wells could be drilled at various locations in andaround the suspected contaminated site to determine, as closely aspossible, where the contamination is located. Core samples would bewithdrawn, being careful to protect the samples from atmosphericoxidation. The samples would be used to determine soil oxidant demandand chemical (i.e. VOC) oxidant demand existing in the subsurface. Theprecise chemical compounds in the soil and their concentration wouldalso be determined. Contaminated groundwater would be collected.Oxidants would be added to the collected groundwater during laboratorytreatability experiments to determine which compounds are destroyed inthe groundwater. It would then be determined whether the same oxidantsare able to destroy those chemicals in the soil environment.

The goal is for the concentration in the injected solution to be justenough to result in the reaction front traveling at the same velocity asthe groundwater in the saturated zone, or as close as possible thereto.(The saturated soil zone is the zone of soil which lies below the watertable and is fully saturated. This is the region in which groundwaterexists and flows.) In certain saturated zones where the natural velocityof the groundwater is too slow for the purposes of treatment within acertain timeframe, the velocity of groundwater can be increased byincreasing the flow rate of the injected persulfate solution orinstallation of groundwater extraction wells to direct the flow of theinjected solution. Certain soils to be treated may be in unsaturatedzones and the method of injection may be based on infiltration ortrickling of the solution into the subsurface to provide sufficientcontact of the soils with the injected chemicals. Certain soils andconditions will require large amounts of oxidants to destroy soiloxidant demand, while other soils and conditions might not. For example,sandy soils having large grain size might have very little surface area,very little oxidizable compounds and therefore very little soil oxidantdemand. On the other hand, silty or clayey soils, which are very finegrained, would have large surface area per unit volume. They are likelyto also contain larger amounts of oxidizable compounds and thus have ahigh soil oxidant demand.

In another embodiment of the invention, activators, such as metals andchelated metal complexes, may also be added either in combination,sequential fashion or multiple sequential steps either to the additionof hydrogen peroxide, the addition of persulfate, or the addition ofboth hydrogen peroxide and persulfate.

Activators which may be used to enhance the effects of thepersulfate/hydrogen peroxide include divalent and trivalent transitionmetals such as Fe (II), Fe (III), Cu (II), Mn (II) and Zn (II). Themetal may be added in the form of a salt or a chelate. Preferredchelants which may be used include ethylenediamine tetraacetic acid,citric acid, phosphate, phosphonates, glucoheptonates,aminocarboxylates, polyacrylates, catechol and nitroacetic acid.

In addition to treatment of soil, the invention is also useful fordestroying contaminants in groundwater, process water, waste water orany other environment in which contaminants susceptible to oxidation arefound.

In order to describe the invention in more detail, the followingexamples are set forth:

EXAMPLE 1

A composition was prepared containing 300 ml deionized water and 150grams of soil—“fill sand” obtained from Nimbus Landscaping Materials,Rancho Cordova, Calif. Approximately 85% of the sand was less than 30mesh (600 microns). The soil contained 3700 mg/kg total organic carbon(TOC) and 17000 mg/kg iron. The composition was placed in a 500 mlglass, amber bottle and was spiked with a 500 ul aliquant, using agas-tight glass syringe, of a methanol stock solution containing MTBE,CT, TCA, TCE and benzene such that the initial concentration of eachchemical was about 20 mg/l. The bottles were capped and placed on ashaker table for three weeks to equilibrate.

A master batch of 200 g/L sodium persulfate aqueous solution wasprepared by dissolving 100 g of sodium persulfate into 500 mL ofdeionized water. Enough of the sodium persulfate solution, withadditional deionized water if needed, was added to the “Persulfate Only”and “Persulfate/Peroxide” test samples to bring the total aqueousvolumes to 350 mL with a persulfate concentration of 5 g/L. In addition,50 g/L of a 17% hydrogen peroxide solution was added to the“Persulfate/Peroxide” test samples. The sample containers were capped,placed on a shaker table, and periodically shaken.

Periodically, one sample from each test group was sacrificed, withapproximately 200 mL of the soil-water mixture quickly decanted into a225 mL centrifuge tube. The sample was then centrifuged at 4400 rpm for5 minutes. A portion of the resultant aqueous phase then was decantedinto HCI-preserved VOA jars. Volatile organic compound concentrationanalysis was then performed utilizing EPA Method 8260B.

The results, in percent of contaminants removed, are shown in Table 1.TABLE 1 Time (days) Control Persulfate Only Persulfate/Peroxide Benzene1 31.9 57.4 77.7 3 13.8 37.2 93.9 8 42.6 85.1 99.7 24 22.3 98.9 100.0Carbon Tetrachloride 1 69.0 19.0 93.3 3 53.4 12.1 94.8 8 77.6 75.9 96.724 81.0 37.9 100.0 Trichloroethane 1 59.3 11.6 81.4 3 44.2 4.7 88.7 8.072.1 66.3 93.8 24 68.6 23.3 99.6 Trichloroethene 1 47.7 45.3 77.9 3 31.429.1 90.9 8 64.0 82.6 99.0 24 46.5 94.9 100.0 MTBE 1 4.1 −9.6 −9.6 3 4.1−9.6 11.0 8 4.1 4.1 32.2 24 4.1 11.0 69.9

EXAMPLE 2

Using the same procedures and materials as in Example 1, batch testswere conducted by adding sodium persulfate and/or H2O2 to 75 g of soiland deionized water that had been spiked with a methanolic solution ofVOCs. The total solution volume was 175 mL, giving a soil to liquidratio of 1:2.3. The initial conditions are given in Table 2A below. Thecontrol, Persulfate Only, Very Low H2O2 tests were capped tightly. TheH2O2 Only, Low H2O2, and High H2O2 tests were loosely capped for thefirst 24 hours (to prevent buildup of pressure due to decomposition ofH2O2); caps we re tightened after 24 hours. TABLE 2A Initial InitialMole Ratio Test ID Na2S208 H2O2 (%) H2O2:Na2S208 Control 0 0 n.aPersulfate Only 10 0 n.a Peroxide Only 0 2.6 n.a Very Low Peroxide 100.01 0.1 Low Peroxide 10 0.65 5 High Peroxide 10 2.6 20

The percent removed for each VOC is given in Table 2B. The percentremoved was calculated from the total mass in the aqueous phase and theheadspace. The concentration in the headspace was calculated from theaqueous concentration and volume of headspace using Henry's law. TABLE2B Very Low High Time Persulfate Peroxide Low Per- Per- (days) ControlOnly Only Peroxide oxide oxide Benzene 1 9.1 42.9 97.1 63.0 96.3 99.9 363.6 67.5 98.9 80.5 99.6 100.0 8 39.0 >99.8 99.4 98.7 100.0 100.0 2391.6 >99.9 99.9 >99.9 100.0 99.9 Carbon Tetrachloride 1 25.8 4.6 99.443.5 97.3 99.8 3 78.8 48.8 99.6 70.0 98.4 99.8 8 55.8 95.2 99.6 78.899.8 99.7 23 98.9 96.6 >99.9 99.4 98.9 99.5 1,1,1-TCA 1 18.3 0.0 99.235.8 94.8 99.7 3 74.2 36.7 99.6 60.8 97.0 99.8 8 48.3 88.3 99.6 65.099.6 99.8 23 97.4 56.7 100.0 86.7 97.7 100.0 TCE 1 14.3 28.6 98.5 55.795.4 99.9 3 70.7 55.0 99.2 71.4 99.1 99.9 8 48.6 99.3 99.4 94.1 100.099.8 23 95.5 >99.8 99.9 >99.9 99.8 99.9 MTBE 1 −3.4 −3.4 50.7 6.4 45.886.7 3 26.1 −13.3 80.3 6.4 60.6 97.3 8 −3.4 16.3 84.7 −37.9 93.1 98.6 2336.0 26.1 94.1 66.0 94.1 99.2

EXAMPLE 3

A composite soil sample was prepared in a steel bowl by combining equalmasses of representative samples of soil collected from a field site.100 gram portions of the composite were transferred to 250 ml amberglass bottles fitted with Teflon lined caps. Treatment of the sampleswas performed by mixing the 100 grams of the soil sample with the amountof chemical corresponding to the treatment dosage (see below). Ten ml ofdeionized water was added to each sample to simulate the amount ofliquid added during a full-scale injection. After treatment, the sampleswere allowed to stand at ambient temperature with the cap looselyattached to the bottle to allow the samples to degas. After eight days,a portion of the aqueous component was removed and analyzed for volatileorganic compounds using EPA method 8260B.

The chlorinated compounds of concern were: methylene chloride, 1,1,1tri-chloroethane and, 1,2di-chloroethane. Results are shown in Table 3.TABLE 3 Treatment A Treatment B Control % % Contaminant μg/kg μg/kgreduction μg/kg reduction Methylene 80,000 82,000 0 25,000 98 chloride1,1,1 3,700,000 2,000,000 46 91,000 98 Trichloethane 1,1 21,000 10,00052 2,500 98 DichloroethaneTreatment A Iron activated persulfate 10 ml of a 20% Na₂S₂O₈ solution +10 mL of a 20% FeSO₄ solution (yields 2 g of each compound per 100 gsoil)Treatment B Iron/Peroxide activated persulfate 10 ml of a 20% Na₂S₂O₈solution + 10 mL of a 20% FeSO₄ solution + 10 mL of a 20% H₂O₂ solution

EXAMPLE 4

Using the procedure described in Example 3, an additional contaminantwas evaluated.

The chlorinated compound of concern was: 1,4 chlorobenzene Results areshown in Table 4. TABLE 4 Treatment A Treatment B Control % %Contaminant μg/kg μg/kg reduction μg/kg reduction 1,4 430,000 160,000 632,500 99 ChlorobenzeneTreatment A Iron activated persulfate 20% Na₂S₂O₈, 20% FeSO₄Treatment B Iron/Peroxide activated Persulfate 20% Na₂S₂O₈, 20% FeSO₄,20% H₂O₂

EXAMPLE 5

Decomposition of Sodium Persulfate in the Presence of Hydrogen Peroxide

Persulfate anions are long lived species and can survive from days,weeks and even months in the subsurface. On the other hand, sulfateradicals are short lived species, and once the persulfate is activatedto form sulfate radicals, the lifetime of the radical species is lessthan one second. Although there may be several decomposition pathwaysfor persulfate, a primary route is the formation of sulfate radicals,and subsequent termination of the radical by combination with otherradicals or organic species. Thus, measurement of the persulfatedecomposition is an indirect determination of the extent of radicalformation.

Combinations of sodium persulfate and hydrogen peroxide were added tosoil—water slurries, and the subsequent decomposition of sodiumpersulfate was measured after three days of reaction time. Soil wasobtained and combined with water at a 50:50 ratio and placed into glassjars. Sodium persulfate and hydrogen peroxide were added to the jars atvarying sodium persulfate concentrations, and hydrogen peroxide tosodium persulfate ratios of 1:10, 1:1 and 10:1. The jars were sealed andplaced in the dark. Analysis of the sodium persulfate concentration wasconducted on day three utilizing persulfate titration methods. Theresults of the study are shown in Table 5. TABLE 5 Initial PersulfatePersulfate Initial Concentration @ Concentration Mole ratio Day 3 %Persulfate (ppm) Na₂S₂O₈:H₂O₂ (ppm) Loss 4000 10:1  3067 23 4000 1:11370 66 4000  1:10 60 99 11000 10:1  7206 34 11000 1:1 1727 84 11000 1:10 89 99 22000 10:1  11434 43 22000 1:1 3335 83 22000  1:10 119 9922000 0 15007 25

Table 1: Persulfate Decomposition as a Function of Peroxide Level

Resilts from Table 5 indicate that as the amount of hydrogen peroxideincreases, the greater the decomposition of the sodium persulfate,indicating increased formation of sulfate radicals with increasingperoxide concentrations. A wide range of persulfate to hydrogen peroxidemay be used in the present invention.

EXAMPLE 6

Using the procedure described in Example 3 additional samples ofcontaminants were treated.

Acid water refers to a 1% aqueous solution of phosphoric acid. When used1 ml of this solution was added with the hydrogen peroxide.

The results are shown in the following tables. TABLE 6A Parameters(ug/kg) Untreated Persulfate H₂0₂ and Persulfate Control with Iron withIron Tetachloroethene 1,800,000 750,000 340,000 Trichloroethene 21,00012,000 1,800

TABLE 6B Parameters (ug/kg) Persulfate H₂0₂ with H₂0₂, Acid Untreatedwith Acid Water, & Composite Iron Water Persulfate 1,1,1- 340,000 57,00015,000 9,200 Trichloroethane 1,1,-Dichloroethene 4,500 550 170 63

TABLE 6C Parameters (ug/L) H₂0₂ with Acid H₂0₂ with Control Sample WaterPersulfate Acid Water Diesel Range Organics 13,000 5,500 7,800

EXAMPLE 7

Using the procedure described in Example 3, samples of contaminants weretreated. The following treatments were used. Treatment A 25000 PPM H2O2100 PPM H3PO4 80 PPM Na₂S₂O₈ Treatment B 25000 PPM H2O2 100 PPM H3PO4

The results are shown in Table 7. ND indicates “none detected” meaningthe amounts were below the limits of detection. TABLE 7 ContaminantControl (PPB) Treatment A Treatment B Trichloroethene 1200 17 99 cis 1,1Dichloroethene 6900 4 370 1,1,1 Trichloroethane 12000 810 1400 11Dichloroethane 1100 ND 250 1,1 Dichloroethene 2100 ND 180Tetrachloroethene 220 ND 124

EXAMPLE 8

Using the same procedure as in Example 7, an additional sample wasevaluated. The results are shown in Table 8. TABLE 8 Contaminant Control(PPB) Treatment A Treatment B Trichloroethene 2800 ND 350

1. A method for oxidizing a contaminant present in an environmentalmedium, said method comprising contacting the contaminant with acomposition comprising a persulfate and hydrogen peroxide.
 2. The methodof claim 1, wherein the persulfate is a monopersulfate or adipersulfate.
 3. The method of claim 1, wherein the persulfate is sodiumbase, ammonium base, or potassium base.
 4. The method of claim 1 whereinthe persulfate is sodium persulfate.
 5. The method of claim 1 whereinthe mole ratio of persulfate to hydrogen peroxide is equal to from 1:20to 20:1.
 6. The method of claim 1 wherein the mole ratio of persulfateto hydrogen peroxide is equal to from 1:10 to 10:1.
 7. The method ofclaim 1 wherein the persulfate and hydrogen peroxide are appliedsimultaneously to the medium.
 8. The method of claim 1 wherein thepersulfate and hydrogen peroxide are applied sequentially to the medium.9. The method of claim 1 wherein the persulfate is applied to the mediumprior to the application of the hydrogen peroxide.
 10. The method ofclaim 1 wherein the hydrogen peroxide is applied to the medium prior tothe application of the persulfate.
 11. The method of claim 1 wherein thepersulfate and hydrogen peroxide are applied to the medium sequentiallyin repeated applications.
 12. The method of claim 11 wherein therepeated sequential additions of persulfate and hydrogen peroxide occurcontinuously.
 13. The method of claim 11 wherein the repeated sequentialadditions of persulfate and hydrogen peroxide are separated by timeintervals.
 14. The method of claim 1 wherein the environmental medium isselected from soil, rock, groundwater, wastewater and process water. 15.The method of claim 1, wherein the oxidation is performed in situ or exsitu.
 16. The method of claim 1, wherein the composition is introducedinto the environmental medium in sufficient quantities and underconditions to oxidize substantially all of the contaminants in themedium.
 17. The method of claim 1 where the composition also includes anactivator.
 18. The method of claim 17 where the activator is a divalentor trivalent transition metal.
 19. The method of claim 18 wherein theactivator is a divalent transition metal selected from Fe (II), Cu (II),Mn (II) or Zn (II).
 20. The method of claim 18 wherein the activator isa trivalent transition metal, iron (III).
 21. The method of claim 17wherein the activator is a divalent or trivalent transition metalcombined with a chelating agent.
 22. The method of claim 21 wherein theactivator is a divalent transition metal selected from iron (II), Cu(II), Mn (II) or Zn (II).
 23. The method of claim 21 wherein theactivator is a trivalent transition metal selected from iron (III). 24.The method of claim 21 wherein the chelating agent is selected fromethylenediamine tetraacetic acid, citric acid, phosphate, phosphonate,catechol or nitroacetic acid.
 25. A composition suitable for use intreating a contaminant present in an environmental medium, saidcomposition comprising a persulfate and hydrogen peroxide.
 26. Thecomposition of claim 25, wherein the persulfate is a monopersulfate or adipersulfate.
 27. The composition of claim 25, wherein the persulfate issodium base, ammonium base, or potassium base.
 28. The composition ofclaim 25, wherein the persulfate is sodium persulfate.
 29. Thecomposition of claim 25 wherein the mole ratio of persulfate to hydrogenperoxide is equal to from 1:20 to 20:1.
 30. The composition of claim 25wherein the mole ratio of persulfate to hydrogen peroxide is equal tofrom 1:10 to 10:1.
 31. The composition of claim 25 further including anactivator.
 32. The composition of claim 31 wherein the activator is adivalent or trivalent transition metal.
 33. The composition of claim 32wherein the activator is a divalent transition metal selected from Fe(II), Cu (II), Mn (II) or Zn (II).
 34. The composition of claim 32wherein the activator is a trivalent transition metal, Fe (III).
 35. Thecomposition of claim 31 wherein the activator is a divalent or trivalenttransition metal combined with a chelating agent.
 36. The composition ofclaim 35 wherein the activator is a divalent transition metal selectedfrom Fe (II), Cu (II), Mn (II) or Zn (II).
 37. The composition of claim35 wherein the activator is a trivalent metal, Fe (III).
 38. Thecomposition of claim 35 wherein the chelating agent is selected fromethylenediamine tetraacetic acid, citric acid, phosphate, catechol ornitroacetic acid.